Fundamental research on selective arsenic removal from high-salinity alkaline wastewater. (November 2022)

• Record Type: Journal Article
• Authors: Wang, Yufeng; Tian, Jia; Peng, Jun; Sun, Wei; Zhang, Xingfei; Han, Haisheng; Shen, Jifeng
• Is Part Of: Chemosphere. Volume 307:Part 3(2022)
• Publication Date: 2022-11
• Subjects: High-salinity alkaline wastewater -- Magnesium ammonium arsenate -- Selective separation; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.135992
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The alkaline leaching process of arsenic-containing solid waste discharged during nonferrous metal smelting affords typical high-salinity alkaline arsenic-containing wastewater (HSAW). In this study, for the first time, Me (Ca 2+ and Mg 2+ )–AsO4 3− –OH − –H2 O and Me (Ca 2+ and Mg 2+ )–AsO4 3− –CO3 2− –H2 O systems are studied based on a thermodynamic equilibrium diagram and an arsenic removal experiment, proving that the removal of arsenic using single metal ions in the presence of CO3 2− is infeasible because of carbonate coprecipitation. Based on this observation, a new method that uses magnesium ammonium complex salts (MACSs) for HSAW treatment is proposed. Based on the thermodynamic calculations of the Mg 2+ –AsO4 3− –NH4 + –CO3 2− –H2 O system and the arsenic removal experiment, carbonate and arsenate can be selectively separated by the formation of magnesium ammonium arsenate (NH4 MgAsO4 ·6H2 O). In an arsenic solution containing 150-g/L Na2 CO3, the arsenic removal rate and the arsenic grade of the precipitation product reach 90.16% and 27.13%, respectively, when the molar ratios of Mg 2+ /NH4 + :As(V) are 1.8:1 and 2:1, respectively. The proposed method is successfully employed for treating a leaching solution of alkaline arsenic slag discharged during antimony smelting. The findings of this study will broaden the basic theory of HSAW treatment and lay a foundation for the resource treatment of arsenic-containing solid waste. Graphical abstract: Image 1 Highlights: The traditional arsenic removal methods were infeasible in Na2 CO3 solution. A method for the selective separation of arsenic and alkali by MACSs was proposed. Arsenic component was precipitated in the form of MgNH4 AsO4 . The theoretical systems of arsenic removal by MACSs were established. Alkaline arsenic slag can be disposed cleanly and safely by the novel method.